Regulator valves (also called pressure regulators) are used in myriad industrial and residential applications for controlling the downstream pressure of a fluid. For example, in chemical processing plants or oil refineries, regulator valves are used to manipulate a flowing fluid to compensate for increases or decreases in demand, or other load disturbances, and thus keep the fluid pressure regulated. Similarly, regulator valves may be used in plumbing fixtures to maintain a pre-determined pressure of fluid that automatically adjusts to variations in demand, such as anti-scald valves in showers or faucets. By controlling downstream pressure, regulator valves compensate for variations in downstream demand. For example, as downstream demand increases, a typical regulator valve opens to allow more fluid to flow there through, thus maintaining a relatively constant downstream pressure. Conversely, as downstream demand decreases, the typical regulator valve closes to reduce the amount of fluid flowing there through, again maintaining a relatively constant downstream pressure.
Typical regulator valves can be categorized as either balanced or unbalanced. Typical unbalanced regulator valves have high pressure inlet fluid on one side (i.e., inlet or upstream side) of the valve plug and lower pressure outlet fluid on the other side (i.e., outlet or downstream side) of the valve plug. In the typical balanced regulator valve, a portion of the upstream fluid pressure is vented to act on a downstream portion of the valve plug so as to at least partially counterbalance the upstream and downstream pressures acting on the valve plug. Thus, the regulator valve is “balanced,” having either the same fluid pressure acting on both upstream and downstream portions of the valve plug or at least a reduced pressure differential between the upstream and downstream portions of the valve plug.
FIG. 1 illustrates a known regulator valve arrangement, including a pressure regulator valve 10, a pilot 12, and a pilot supply filter regulator 14. The pilot 12 and the pilot supply filter regulator 14 are operatively connected with the outlet fluid stream and the pressure regulator valve 10 so as to provide a desired fluid pressure in the outlet fluid stream, in a manner understood in the art. In this arrangement, the regulator valve 10 includes a balanced valve trim assembly, as described generally hereinafter.
FIG. 2 illustrates a detailed exemplary arrangement of the regulator valve 10. The regulator valve 10 includes a valve body 16, an actuator 18 connected to the valve body, and a balanced valve trim assembly 20. The actuator 18 controls the position of the balanced valve trim assembly 20 within the valve body 16 so as to regulate the flow of fluid through the valve body. The actuator 18 moves a flow control member 32 between a fully open state, in which the maximum amount of fluid possible passes through the regulator valve 10, and a fully closed state, in which no fluid passes through the regulator valve 10, in response to the downstream fluid pressure exiting the regulator valve 10.
The valve body 16 defines a fluid flow path extending through an orifice or valve throat 26 and from an inlet 22 to an outlet 24. Further, a bonnet 25 operatively couples the actuator 18 to the valve body 16.
The valve trim assembly 20 includes a seat ring 28, a cage 30, and a flow control member 32. The seat ring 28 is disposed at the valve throat 26 and adapted to form a valve seat. The cage 30 affects the flow of fluid on the downstream side of the valve trim assembly 20, for example by reducing cavitation, improving laminar flow, and/or providing noise control. The flow control member 32 is arranged to move between the open position, in which a valve disk assembly is spaced apart from the seat ring 28, and the closed position, in which the valve disk assembly 34 is sealed against the seat ring 28, so as to control the flow of fluid through the valve throat 26. In this arrangement, the flow control member 32 includes the valve disk assembly 34, a sleeve adapter 36, and a sleeve 38. The valve disk assembly 34 includes a seal that sealingly engages the seat ring 28 when the flow control member 20 is in the fully closed position. The sleeve 38 forms a valve stem that operatively connects the valve disk assembly 34 with the actuator 18. The sleeve adapter 36 couples the valve disk assembly 34 to the sleeve 38.
The actuator 18 includes a diaphragm assembly 40, which is operatively disposed within an actuator housing 42 and operatively coupled to the sleeve 38. The actuator 18 is operatively coupled with the outlet fluid stream via the pilot 12 and the pilot supply filter regulator 14 so as to cause the diaphragm assembly 40 to move up and/or down within the actuator housing 42 in response to the fluid pressure at the outlet 24 of the valve body 16. In this arrangement, the actuator includes a spring 41 that pushes against one side of the diaphragm assembly 40, whereas the opposite side of the diaphragm assembly is exposed to the downstream fluid pressure exiting the regulator valve 10. The diaphragm assembly 40 is coupled to the sleeve 38 such that the diaphragm assembly 40 moves the sleeve 38 up and/or down along with the movement of the diaphragm assembly 40.
The sleeve 38 is in the form of an elongate hollow tube, preferably having a circular cylindrical shape, extending from a lower to an upper end. The sleeve adapter 36 is disposed in and fixed to the lower end of the sleeve 38, and the valve disk assembly 34 is fixedly coupled to the sleeve adapter 36. The upper end of the sleeve 38 is slidingly received within a blind bore formed in the top portion of the actuator housing 42. The lower end of the sleeve 38 is slidingly received through a through bore formed in the bottom portion of the actuator housing and aligned with the valve throat 26. The lower end of the sleeve 38 slides axially along the through bore, and the upper end of the sleeve 38 slides axially along the blind bore. Further, the exterior surface of the sleeve 38 is sealingly engaged against the interior surface of each of the through bore and the blind bore, such as with seals 43, so as to fluidly isolate the interior of the sleeve 38 from the rest of the interior of the actuator housing 42. Each of the valve disk assembly 34 and the sleeve adapter 36 has a centrally and axially aligned orifice, which together define a passageway 44 that fluidly couples the fluid flow path of the valve body 16 to the interior of the sleeve 38. Thus, the passageway 44 fluidly couples the upstream and the downstream sides of the valve disk assembly 34, which balances the fluid pressures on opposite sides of the valve disk assembly 34, thereby providing a balanced valve trim assembly.
FIG. 3 shows the sleeve 38, the sleeve adapter 36, the valve disk assembly 34, and the seat ring 28 in isolation. As illustrated by arrow A, fluid from the inlet 22 passes through the seat ring 28 (and thus also the throat 26) and through the passageway 44 defined by the sleeve adapter 36 and the valve disk assembly 34 into the interior of the sleeve 38, thereby equalizing pressure on opposite sides of the valve disk assembly 34.
In such a known regulator valve arrangement, the regulator valve 10 is preferably sized such that the application requirements of the entire arrangement are met within a preferred operating range somewhere near the middle of the travel distance of the closure member 32 without the need to operate the regulator valve 10 too close to either travel extreme of the valve trim, i.e., with the flow control member 32 either at or particularly near the fully open state or at or very near the fully closed state. In some arrangements and/or under some operating conditions, the regulator valve 10 may be too large for the expected operating conditions. This may occur, for example, if the operating conditions are changed after the regulator valve has already been installed along a pipeline. This may cause the flow control member 32 to operate very close to the valve seat 28 under the new expected operating conditions. If the flow control member 32 has a soft seat, such as a soft valve disk or plug, this condition can cause damage to the seat material, which in some cases could prevent the regulator valve from shutting off as necessary. Although this condition in some circumstances might be addressed by providing a smaller valve, this solution is often not viable for other practical considerations.
One way of adjusting the effective size of the balanced valve trim assembly to address this condition of having an oversized regulator valve is to install a smaller valve seat at the valve throat 26. The drawback of this strategy, however, is that they cannot be as effectively utilized under operating conditions that run at higher pressures, apparently due to imbalances caused by the smaller valve seat.